Progress in Optics

This volume presents five review articles covering a broad range of topics which will be of interest to many scientists concerned with optics and related subjects.The first article deals with nonlinear optical properties of chalcogenide glasses. These materials have many interesting structural properties, some of which are useful for applications to integrated active optical devices. This article presents a review of experimental measurements of nonlinear absorption coefficients and nonlinear refractive indices of such materials. A review of various models formulated to explain their properties is also included.The next article reviews the research on super-resolution, i.e. the possibility of overcoming the classical diffraction limit of about half a wavelength. The problem is shown to be essentially equivalent to extrapolating the spatial frequency spectrum of the object beyond the spectral band of the optical system.